--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -634,9 +634,11 @@ def diff(ui, repo, *pats, **opts):
raise Abort("too many revisions to diff")
files = []
- roots, match, results = makewalk(repo, pats, opts)
- for src, abs, rel in results:
- files.append(abs)
+ match = util.always
+ if pats:
+ roots, match, results = makewalk(repo, pats, opts)
+ for src, abs, rel in results:
+ files.append(abs)
dodiff(sys.stdout, ui, repo, files, *revs, **{'match': match})
def doexport(ui, repo, changeset, seqno, total, revwidth, opts):